1. Field of the Invention
The present invention is directed to a device for collecting water from air and more particularly, to a device for collecting the moisture contained in the atmosphere and condensing it into water of high purity.
2. Related Art
Several devices have been previously described for making water from moisture in the atmosphere. For the sake of simplicity, these devices are termed herein “water-makers.” Typically, these systems are based on a refrigeration device operating according to the vapor compression refrigeration cycle. They are known from other applications as dehumidifiers. In the vapor compression refrigeration cycle, a refrigerant is circulated through a closed circuit cycle of condensation and evaporation to produce a cooling effect. Cooling is accomplished by the evaporation of the liquid refrigerant at low pressure. The refrigerant first enters a compressor, where the temperature of the refrigerant is elevated by mechanical compression, turning the refrigerant into a superheated, high pressure vapor. The high pressure vapor enters a condenser, where the vapor condenses to a liquid and the resultant heat is dissipated to the surroundings. The resultant high pressure liquid then passes through an expansion valve through which the fluid pressure and temperature are lowered. Finally, the low-pressure fluid enters the evaporator, where it evaporates by absorbing heat from the cooled space. The resultant vapor then reenters the compressor and the cycle is repeated. As air flows across the evaporator, it is cooled below its dew point. Thus, water, in the form of condensation, is obtained as a byproduct of the vapor compression refrigeration cycle. A condensed water collection device is disposed below the evaporator to collect water than condenses as air flows over the evaporator.
Often, these water-makers are also equipped with various devices for water storage and for maintaining and controlling water purity, such as UV lights and filters. Conventional water supply devices, such as water fountains and dispensers for spring water, are designed to provide water that is either cooled or heated for the convenience of the user.
The prior water-makers all have in common that the preferred operating mode requires air of high moisture content which is readily available in high temperature/high humidity climates. For most devices, the operating range begins at 65° F. and 50% relative humidity and ranges to higher temperatures. If the temperature drops below 65° F., the evaporator coil will show frost accumulation and eventually be covered by a solid block of ice. Under low temperature conditions, the water production rate is very low or zero and the power consumption is very high. The effectiveness of the system, expressed in liters of water per kWh of electricity consumed is very low or zero and accordingly the operating cost unacceptably high.
The inefficiency of the conventional systems results from the fact that for each pound of water produced, a large amount of air has to be cooled below the dew point. The colder the air temperature, the lower the water content and the lower the dew point. Consequently, more air has to be cooled before any moisture is condensed. This leads to very large evaporator capacities that do not contribute to the production of water per se.
However, once a user has a water-maker in operation, he will expect water production even under colder and dryer conditions. Thus, there is a need for a more reliable device, the water production capability of which is not so sensitive to weather and environmental conditions. This is especially important for applications in deserts, military uses and the like, where no other back-up water source may be available.